In recent years, input apparatus such as operation units, switches and the like having touch sensors such as touch panels, touch switches and the like to receive input operations by users have been widely used for mobile terminals such as mobile phones and gaming machines, information equipment such as calculators and ticket vending machines, home electric appliances such as microwaves, TV sets and lighting equipment, industrial equipment (FA equipment) and the like.
There are known a variety of types of those touch sensors, such as a resistive film type, a capacitive type, an optical type and the like. However, touch sensors of these types receive a touch input by a finger or a stylus pen and, unlike push-button switches, the touch sensors themselves are not physically displaced even when being touched.
Since the touch sensors themselves are not physically displaced when touched, an operator may not obtain feedback to an input even though the touch input is received. As a result, the operator is likely to input erroneously by touching the same spot multiple times, which may be stressful for the operator.
As methods to prevent such erroneous inputs, there are known methods to visually or auditory confirm the input operations by, for example, generating sounds or by changing a display state, such as colors of input objects such as input buttons and the like graphically depicted in a display unit, according to an input position upon reception of the touch input.
However, such auditory-appealing feedback may be difficult to be confirmed in a noisy environment and is not applicable when the equipment being used is in a silent mode. In addition, in using such visually-appealing feedback, if the input object displayed in the display unit is small, the operator may not be able to confirm the change in the display state, as a view of the input object is blocked by a finger, when the operator is inputting by the finger.
There is also suggested a feedback method relying on neither the auditory-nor visual sensation but instead generating a tactile sensation at operator's fingertip by vibrating the touch sensor when the touch sensor receives an input (for example, see Patent Documents 1, 2).